Antibacterial reactions of cultured insect cells (Blattella germanica) to symbiotic bacteria and microsporida will be characterized by studying the processes of adsorption, phagocytosis, and activation of lysosomal machinery. Mycetocytes from nymphal fat bodies, from ovarian sheaths, and from young embryos will be cultured in serm-free medium containing cholesterol and lecithin. Isolated symbiotic bacteria will be cultured in serum-free-medium with high K:Na ratios and with low oxygen tension. The effect of vitellogenin and juvenile hormone on development (regulation) of ovarian symbiotes and mycetocyte symbiotes will be examined with in vitro organ cultures. Studies regarding the mode of symbiote infection, i.e., the stage at which symbiotes enter mycetoblasts and the stage at which they enter ovaries, will be continued. Symbiote survival in transformed cells will be compared to that in primary cultures.